Small objects such as pills, capsules, and tablets are typically produced in bulk but packaged by placing them each in a respective pocket or blister of a plastic packaging strip. Thus the process entails the steps of separating the pills from each other, positioning them in an orderly array, and then transferring them from this array to the respective pockets of the packaging strip. Another plastic film or metallic foil is then bonded on top of the thus filled packaging strip, and the laminate thus formed is cut into individual packages each normally having a plurality of blisters, although it is possible for a package to have only one blister.
The sorting and arraying step is relatively easy. The objects are deposited on a slightly inclined and relatively broad feed plate that is vibrated such that the objects orient themselves in a single layer. The lower outlet end of the vibrating feed plate deposits them gently on a slowly moving conveyor formed with an array of upwardly open pockets typically arrayed identically to the blister pockets of the packaging strip to be loaded. The pockets of this conveyor are dimensioned such that they can each just hold a single one of the objects, and the conveyor is vibrated also so that the objects work their way into the pockets, filling them all. A scraper oriented somewhat downstream along the path of the conveyor pushes the excess objects off the upper surface of the conveyor and recirculates them back to the upstream end of the process, so that downstream of the scraper the conveyor is transporting an exactly ordered array of the objects, one in each pocket.
At a loading station at the downstream end of the conveyor a transfer device comprising a multiplicity of suction grabs oriented identically to the conveyor pockets drops down on the conveyor, which can move slowly continuously or in steps, and picks out all the objects from a short length of the conveyor, then swings normally further downstream and deposits the picked-up objects into the pockets of the packaging foil, which typically is moving in steps transversely past the downstream end of the conveyor. Once a section of the conveyor has been emptied, it is recirculated back to the upstream conveyor end at the downstream end of the vibrating feed plate and gets reloaded as described in German patent 10 2005 049 882 issued 1 Feb. 2007.
The problem with this system is that the recirculation of the feed plated is fairly complicated. At the loading station the plates are dropped down by a special device having its own actuator and engaging it on the downstream and of a conveyor belt that then shifts the dropped plate back upstream where it is transferred to another special device that raises it up to the feed level, where it forms the downstream end of a succession of such plates that are pushed downstream, normally in steps. This mechanism is fairly complicated and raises the cost of the machine and increases service problems. The three separate drives necessary for moving the feed plates back upstream must be perfectly synchronized, and any minor failure brings the entire equipment down.